Manometer



Jan. 7,1941. c. P. ABBERT 2,228,023,

MANOMETER Filed NOV. 3, 1939 INVENTOR. CLAUDE I? ABBERT BY A9 7 ATTORNEY.

Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE 2,228,023 MANOMETER Application November 3, 1939, Serial No. 302,734

4 Claims.

This invention relates to manometers and particularly to manometers useful for the determination of blood pressure.

It has been the practice to provide a closure for the upper or open end of the indicating tube of a sphygmomanometer of the mercury type, which would allow air to pass into and out of the indicating tube with the fall and rise of the mercury column but which prevented the loss of mercury through the closure. The known closures include a sheet or disk of barometer kid which is. sufiiciently porous to allow air to leak therethrough but which is impervious'to mercury. The barometer kid closures have not proven entirely satisfactory in that they introduce a lag in the instrument, since while the barometer kid permits air toypass therethrough it nevertheless retards the flow of the air into and out of the space within the indicating tube above the mercury column. Thus, if insufficient time were allowed for the mercury column to reach its true position, that'is, when the space'above the mercury column reaches atmospheric pressure, a false reading of the blood pressure would be obtained. To overcome this disadvantage and to decrease the time required to obtain an accurate reading of the blood pressure, it is a purpose of the present invention to provide a closure for the open end of the indicating tube which allows air to flow therethroug'h at a much greater rate than possible with known instruments.

It is therefore an object of this invention to provide an improved sphygmomanometer including a closure through which air is free to flow from within the tube portion but which prevents the leakage of mercurytherethrough.

It is anotherobject of the invention to provide an improved closure for the indicating tube of a sphygmomanometcr includinga sheet of barometer kid which has a greater effective area for the leakage of air therethrough than in prior instruments of this class.

It is still another feature of the invention to provide a closure of the character mentioned which is easily removed and dismantled to facilitate cleaning and replacement of the barometer kid.

These and other objects of the invention will appear from the detailed description and claims when taken with the drawing in which Fig. 1 is: a perspective view of a sphygmomanometer made in accordance with the present invention; Fig. 2 is a face view of the manometer proper, portions thereof being shown in section to illustrate details of construction; and Fig. 3 is an exploded view of the closure for the upper'end of the indicating tube, the parts being shown in section.

Referring to the drawing, the numeral 5 gena steel reservoir 8 for mercury or the like, which fixture is provided with a passageway 9 leading from the reservoir to a recess it in the upper face of the fixture. The upper end of the reservoir 8 terminates in a nipple ii. This nipple has connected thereto, by a rubber tube l2, an inflatable cufi i3 which can be inflated by a well-known pump or hand-bulb M. A removable indicating tube 15 rests in the recess Iii andis in liquid-tight connection with the passageway 9, being pressed firmly on the cork or other suitable washer HS as will appear hereinafter.

The'upper end of the indicating tube projects into a threaded opening ll in'a bracket I8 suitably secured to the instrument case cover. If

desired this bracket may be formed integral with h the graduated scale plate i9, secured to the cover 6, in back of the indicating tube. The opening I 1 receives the lower end of a fitting 20, the fitting being screwed into the bracket and having a recess 2| in which the upper end of the indicating tube is received. A cork or other suitable washer 22 disposed within the recess, seals the tube in liquidtight relation with respect to the fitting. It will be evident that by turning the fitting Zi'i into the bracket IS, the indicating tube is pressed into liquid-tight engagement with each of the sealing washers l6 and 22.

The fitting is enlarged at its upper end and is provided with an outwardly flaring passage 23 which communicates with the recess 2!. The diameter of the flared end of this passage is preferably twice the diameter of the bore of the indicating tube. The upper surface of the fitting is preferably flat and provides an annular seat 24 surrounding the flared end of the passage 23. An internally threaded cap 25 is provided with a corresponding annular seat 26. The enlarged end of the fitting is externally threaded as indicated at 21 to detachably receive this cap. A sheet or disk 23 of barometer kid is supported on the annular seat 24 over the flared end of the passage 23, being securely held thereto by the annular seat 26 of the cap. A screen 29 of substantially the same diameter as the flared end of the passage 23 is disposed within the recess 30 of the cap to prevent the upper surface of the barometer kid from being closed by contact with the cap, thereby allowing air to pass freely through the barometer kid. The cap is perforated at 3| to allow air to pass through the cap and the barometer kid. To facilitate assembly of the closure, the outer rim of the cap is preferably knurled and the lower end of the fitting is provided with diametrically opposed screw driver receiving slots 32.

The barometer kid is of such character, that while it allows air to pass therethrough, it is impervious to mercury and prevents it from escaping through the cap opening. It will be appreciated that by having the openingthrough the cap tapered outwardly as shown in Figs. 2'

and 3, to a diameter approximately twice that of the bore of the indicating tube, the efiective area of the barometer kid through which air is free to pass, is approm'mately four times as great as the cross-sectional area of the indicating tube. This large effective area of the barometer kid allows air to pass readily therethrough and reduces the lag present in known instruments of this character, where the efiective area of the barometer kid was equal to or less than a crosssectional area of the bore of the indicating tube.

I claim:

1. In a manometer, a reservoir having a pressure connection nipple at its upper portion, mercury or the like in said reservoir, a fixture joined to the lower portion of said reservoir and having a bore' therethrough communicating with the interior of said reservoir, an upright transparent indicating tube having one end mounted in fluidtight relation on said fixture with the bore of said tube communicating with the bore in said fixture, and a filter closure in liquid-tight relation with the other end of said tube whereby air will readily pass through the filter but the passage of mercury is prevented, said closure comprising a fitting having a recess therein to receive said other end of the tube, said fitting also having a passage therethrough leading from said recess, said passage flaring outwardly to provide an opening bounded at its largest diameter by an annular seat on said fitting, the internal diameter of said seat being materially greater than the diameter of the bore of said tube, a filter sheet, and means for securing the entire margin of said filter sheet in liquid-tight relation to said seat.

2. In a manometer, a reservoir having a pressure connection nipple at its upper portion, mercury or the like in said reservoir, a fixture joined to the lower portion of said reservoir and having a bore therethrough communicating with the interior of said reservoir, an upright transparent indicating tube having one end mounted in fluidtight relation on said fixture with the bore of said tube communicating with the bore in said fixture, and a filter closure in liquid-tight relation with the other end of said tube whereby air will readily pass through the filter but the passage of mercury is prevented, said closure comprising a fitting having a recess therein to receive said other end of the tube, said fitting also having a passage therethrough leadingfrom said recesssaid passage flaring outwardly to provide an opening bounded at its largest diameter by an annular seat on said fitting, the internal diameter of said seat being materially greater than the diameter of the bore of said tube, a filter sheet having its entire margin in liquid-tight relation to said seat, a perforated cap fastened on said fitting and serving to cover said opening, said cap having a projecting annular seat of approximately the same internal diameter as and registering with said first annular seat, said seats serving to clamp the margins of said filter sheet therebetween in liquidtight relation, the perforation through said cap Ibeing of substantially smaller area than the area defined by said projecting annular seat.

3. In a manometer, a reservoir having a pressure connection nipple at its upper portion, mercury or the like in said reservoir, a fixture joined to the lower portion of said reservoir and having a bore therethough communicating with the interior of said reservoir, an upright transparent indicatirig tube having one end mounted in fiuidtight relation on said fixture with the bore of said tube communicating with the bore in said fixture, and a filter closure in liquid-tight relation with the other end of said tube whereby air will readily pass through the filter but the passage of mercury is prevented, said closure comprising a fitting having a recess therein to receive said other end of the tube, said fitting also having a passage therethrough leading from said recess, said passage flaring outwardly to provide an opening bounded at its largest diameter by an annular seat on said fitting, the internal diameter of said seat being materially greater than the diameter of the' bore of said tube, a filter sheet having its entire margin secured in liquid-tight relation to said seat, a perforated cap fastened on said fitting and serving to cover said opening, said cap having a projecting annular seat of approximately the same internal diameter as and registering with said first annular seat, said seats serving to clamp the margins of said filter sheet therebetween in liquid-tight relation, the area within said projecting annular seat being substantially greater than the cross-sectional area of the perforation through said cap, and a perforated disk mounted within the annular seat of said cap adjacent said filter sheet.

4. In a manometer, a reservoir having a pressure connection nipple in the upper portion, a transparent indicating tube having one end thereof communicating with said reservoir, said tube having a bore therethrough of substantially uniform cross-section throughout its length, an indicating. liquid such as mercury in said reservoir, and a filter closure for the other end of said tube whereby the escape of mercury is prevented therethrough but air will pass readily, said closure comprising a perforated fitting engaging the upper end of said tube in liquid-tight relation, with the perforation through said fitting communicating with said bore, a portion of the perforation having a cross-sectional area materially larger than any cross-sectional area of the bore of said tube, a sheet of filter material extending across said perforation at said portion and having its entire edge joined in liquid-tight relation to said fitting whereby each exposed surface of said filter sheet for the passage of air therethrough into said tube is materially larger than any cross-sectional area of the bore of said tube.

CLAUDE P. ABBERT. 

